The overall research objective of this laboratory is to understand the mechanism of regulation of cytochrome P450IA1, a monooxygenase that functions in the activation of polycyclic hydrocarbons, such as benzo (a) pyrene (BP). We have postulated that a cytosolic 4S polycyclic hydrocarbon-binding protein functions as a trans-activator of the P45OIA1 gene. The specific aims of this proposal relate to this hypothesis. The specific aims are to: a) determine the amino acid sequence of the 4S polycyclic hydrocarbon-binding protein, produce polyclonal antibodies to this protein, and determine if phosphorylation and/or conjunction with hsp90 can modify its activity; b) ascertain the nature of the 5'-upstream regions of the P450IA1 gene to which the 4s protein binds, i.e., polycyclic hydrocarbon responsive elements (PRE's), and establish by in vitro nuclear transcriptional assays that the 4s protein is a trans-activator of this gene; c) isolate the 4s protein gene from liver cDNA and genomic libraries and characterize this gene, and d) determine the effects of transfection of vectors that would transcribe antisense to the 4s gene and of introduction of antibodies to the 4s protein on the induction of the P450IA1 gene in response to BP treatment. These studies should establish a central role for the 4s polycyclic hydrocarbon-binding protein in the regulation of the expression of the P450IA1 gene.